Bar-mills used more particularly for the preparation of inks and paints



May 16, 1967 J. M. A. BRlZON BAR-MILLS USED MORE PARTICULARLY FOR THE PREPARATION OF INKS AND PAINTS Filed May 21, 1964 2 Sheets-Sheet 1 w w ,T a o w M /W w u a k 2 f I x w M mflw w W a b ,w m 3' Fig.:2

May 16, 1967 J. M. A. BRIZON 3,319,893

BAR MILLS USED MORE PARTICULARLY FOR THE PREPARATION OF INKS AND PAINTS Filed May 21, 1964 2 Sheets-Sheet 2 Fig. 4

United States Patent 5 Claims. or. 241-241 In US. Patent No. 3,206,129, the present inventor has described an improvement in bar-mills, more particularly in mills having a single cylinder, which consists of using a bar provided with a groove along its whole length, the said groove forming with the cylinder a cavity closed at its extremities and supplied with pulp under pressure by means of a pump. During the course of his tests, the inventor had however first found that the introduction of a certain volume of pulp into the cavity of the bar was particularly necessary at the beginning of the grinding operation, and could be effected by a pump with automatic stopping of the type employed for lubricants, after which the cylinder carried away in its movement sumcient pulp to fill the groove by its own natural action, the pressure in the groove being spontaneously stabilized.

While the means thus employed in order to obtain a high degree of fineness of grinding in a single pass, without either filtration of the coarsest pigments or risk of seizure are particularly simple, which gives a considerable industrial advantage to the invention, it is none-theless true that the carrying away of the pulp into the cavity by the cylinder results in a hydraulic counter-pressure which tends to lift the bar. This counter-pressure is necessary in order to permit the simultaneous achievement, in accordance with the invention, of a high degree of fineness and a large output from the mill, without seizure. It must, however, be very precisely determined, according to the nature and the viscosity of the pulp to be ground.

The force which tends to lift the bar under the effect of the hydraulic counter-pressure in the cavity is directly proportional to the surface area of the groove, and therefore to the width of the groove for a given cylinder.

In the patent referred to above, the widths of the cavities cited in the first place as an example, varied between 1 and 5 millimeters for bars having a maximum width of 15 millimeters, which corresponded to a ratio between the total width of the lips of the bar and that of the cavity amounting to 14/l=14 to l0/5=2. For this reason,

it was necessary to inject pulp under pressure by means of a pump into the cavity in order to counter-balance at least partially the clamping force of the bar and to cause the lifting of the bar, in a continuous manner or in any case during the starting-up of the grinder, and also by way of an added pressure when the said counter pressure was accidentally reduced. The regulation of this counter-pressure was thus obtained by the injection of pulp under pressure by means of the pump.

During the course of tests, the inventor had also found that with a somewhat wider cavity8 millimeters (but still in a relatively narrow bar of 16 millimeters in width, which corresponded to a ratio of unity), on condition that the pulp to be ground had a suitable viscosity, it was possible to obtain spontaneously the pressure necessary to produce lifting of the bar, enabling fineness and high output to be obtained without risk of seizure.

In this latter case however, no regulation was possible except a variation of the composition and the viscosity of the pulp. More precisely, a very exact regulation of the grinding formula was necessary, depending on the 3,319,898 Patented May 16, 1967 nature of the pigments, which limited the possibilities and the ease of use of the mill.

According to the present invention, there is deliberately employed a very wide bar millimeters for example), which can in consequence be provided with a cavity which is also very wide. During the course of a test, the width of the said cavity reached 40 millimeters, that of the lips having a total of only 10 millimeters, which corresponds to a ratio between the total width of the lips of the bar and that of the cavity which is less than unity and may fall as low as 1/4. The cavity was thus finally up to 40 times wider than during all the first tests which led to the filing of the above-mentioned patent. The deliberate choice of a cavity which is wider than the lips which enclose it has the result, for a mill in which the bar is clamped in position by means of hydraulic jacks and in the absence of any device for controlling the counter-pressure of the pulp in the cavity of the bar, of a substantial spontaneous lifting of this bar which finally leads to a considerable output without any risk of seizure, but with imperfect grinding.

This spontaneous lifting is therefore too large, but its control makes it easy to obtain all the desirable adjustments, irrespective of the viscosity of the pulp and the clamping force of the bar against the cylinder due to the hydraulic jacks. This force can thus be given considerable and unusual values without disadvantage, and this also without it being necessary to increase artificially the pressure of the pulp introduced into the cavity. On the contrary, according to the present invention, it is very important to note that the exact value of the counterpressure existing at any point in the cavity is regulated with great accuracy to a value less than that which would naturally tend to be established in the cavity. The regulation thus obtained is faithful but it requires great accuracy, which makes it impossible to achieve with ordinary technical means.

This result is obtained by creating and controlling very precisely a leakage flow out of the cavity of a bar provided with a wide groove, the surplus of pulp fed into the said cavity by the rotation of the cylinder being returned to the hopper when so desired, the counter-pressure diminishing as a function of the magnitude of this leakage flow and in consequence being capable of being brought to the most favourable value to obtain at the same time a high degree of fineness and a high output.

A first means for cont-rolling the leakage flow may be simply constituted by a valve with micrometric regulation, preferably arranged on a conduit which returns the pulp to the hopper. This valve is associated with a pressure-gauge enabling the pressure of the pulp in the cavity to be maintained at the value which corresponds exactly to the desired fineness.

This regulation may advantageously be automatic and not manual only, for example by means of an elastic diaphragm subjected to the counter-pressure of the pulp and coupled to the moving part of the valve, which thus becomes self-regulating.

A second regulating means rests on the fact that a barmill, the cylinder of which carries away the pulp by adhesion at a thickness determined by the clamping pressure of the bar, may be considered as a volumetric machine. The regulation of the pressure to a value different from that which is spontaneously established in a closed cavity in the said bar (which can be determined by a pressure gauge and which results from the leakages under the lips of the bar, these leakages depending in turn on the width of the lips) may be obtained by utilizing a volumetric pump having an output which is a fraction of that of the mill, which is coupled to a suction conduit terminating in the cavity in the bar and which preferably discharges into the hopper. This pump is preferably of the gear type and may be mechanically driven by the rotating cylinder of the mill, but it may alternatively be provided with its own driving means. Its output may be made variable by modifying its speed and even when so required by modification of its unitary volume as a function of the back-pressure in the cavity.

It will of course be understood that the pressure regulation which it is thus possible to obtain manually in a very simple manner may also make use of more complex devices controlling the pump which regulates the liquid flow in dependence on the back-pressure which exists in the cavity.

The bar is generally rigidly fixed to a hopper located above the cylinder and containing the pulp to be ground, which flows by gravity through a port or interstice existing between the hopper and the cylinder along the greater part of a generator line of the said cylinder, except necessarily at the extremities of the hopper at which the latter bears on the cylinder. The result is that a grinding bar is not generally supplied with pulp up to its two extremities, properly so-called, at which there is all the more risk of occurrence of seizure at high degrees of pressure of the bar against the cylinder. Although the invention permits these risks to be substantially reduced, including at the extremities, the inventor determined to make use of the pulp in course of grinding contained in the cavity of the bar to lubricate the extremities of the said bar, even beyond the width of the supply from the hopper.

This result is obtained by reducing the thickness of the curved lips located at the extremities of the bar, and also the thickness of the straight input lip of this bar outside the zone corresponding to the delivery port of the hopper. The output lip of the bar may be given a constant width over the entire length of the bar without any disadvantage, since it is thus supplied almost up to its extremities by the ground product passing out of the cavity in the bar.

Means such as the above, employed in combination, and the operation proper to a bar-mill with a single cylinder, according to the present invention, the natural backpressure in the cavity being capable of regulation with precision, which excludes all risk of seizure even at the extremities of the bar while ensuring the fineness of grinding and high output for such a mill, clearly distinguish this latter from conventional bar-mills with a single cylinder and a single or double bar.

The description which follows below with reference to the accompanying drawings, which are given by way of example and without any implied limitation, will make it easy to understand the various particular features of the invention and the manner in which they are carried into effect.

FIG. 1 is a vertical section of a grinder in accordance with the present invention, provided with a volumetric regulating pump and a pressure gauge.

FIG. 2 is a perspective view of a bar with a cavity and a pressure gauge according to the invention, turned over and partly cut away in order to show the regulating valve and the particular shape of the extremities of the groove with which it is provided.

FIG. 3 is an enlarged diametral section of the valve shown in FIG. 2.

FIG. 4 also shows an alternative form of the selfregulating valve.

Referring to FIG. 1, there can be seen in vertical section a paint mill which comprises an offset hopper 2 and a bar 4 arranged at the upper part of the cylinder 1. This bar is provided with a groove which extends over its entire length and forms a cavity 9 with the surface of the cylinder. The bar is applied against this cylinder in a manner known per se by the pressure of a fluid acting on a number of jacks 5, 6, distributed along its length and provided with a common source of supply (not shown). A scraper device 5 is arranged at the lower part of the cylinder.

A gear-pump 10;, driven in rotation by the cylinder 1 at an appropriate speed, for example by means of two toothed wheels 21, 22 connected together by a chain 23, is provided with an input conduit 11 which terminates in the cavity 9 of the bar 4f, and an outlet conduit 12 which preferably delivers into the hopper. The easy modification of the diameter of the toothed wheels 21 and 22 enables the speed of rotation of the pump and therefore its output to be adjusted to the nature of the pulp in course of grinding (viscosity of the binder, mean size and hardness of the pigments in particular).

In an alternative form of construction, the pump can be directly driven, its output always remaining very small as compared with that of the mill, by means of a small electric motor which may have several speeds of operation, if so required.

A pressure gauge 29] is preferably provided on the bar and put into communication with the cavity 9 or, which. comes exactly to the same thing, in view of the relative magnitudes of the pressures and losses of pressure due to the conduit system, on the suction conduit 11 of the pump 10 The provision of this pressure gauge not only makes it possible to verify the uniformity of the pressure in the cavity of the bar and the correct operation of the grinder, but also the fluid tightness of the pump and its supply conduits and the proper running-in of the bar.

The cleaning of the device is facilitated by the pump 10f if the groove 9 of the bar is provided with a cock at its extremity opposite to the conduit 111. In fact it is only necessary to open this cock and to run the pump while supplying the groove with a small quantity of a solvent such as white spirit to clean the cavity, the pump and the piping system. The solvent is delivered into the hopper and also permits this latter to be cleaned.

It will be clear that the provision of a discharge pump having an insufficient output will result in a back-pressure in the cavity of the bar sufiicient to overcome the clamping pressure and to move the bar away from the cylinder, which would make it difficult to obtain a very high degree of fineness. On the other hand, if the leakage flow were to great, conditions would return to those of the conventional system of double-bar grinders, which run an increased risk of seizure. A pump of suitable output permits on the contrary a pressure to be obtained in the cavity which is stable and which has a fairly low value (2 to 10 kg./sq. cm. for example) which permits the exact clamping force to be applied on the bar, corresponding to the maximum fineness, at the same time however remaining sutficient to avoid all risk of seizure.

FIGS. 2 and 3 relate to an alternative form of construction, very advantageous by reason of its great simplicity of construction, according to which the regulation of the pressure in the groove 9 of a bar 4g is obtained by means of a pressure gauge 26 and a micrometric valve which has the general reference number 24. The bottom of the groove 9 is provided for that purpose with an orifice 25, preferably of elongated section, which communicates with a bore 26 bringing back the excess of pulp to the hopper arranged against the rear face 27 of the bar 4g. In the bore 26 can move a ground rod 26a, on which an axial displacement can be impressed by means of the combination of a nut 28 rigidly fixed to the bar 4g and a threaded rod 26b coupled to the rod 26a. A knurled knob 29, rigidly fixed for rotation with the rod 26a and a dog 3%} fixed for translation with the said rod, but prevented from rotating by a lug 31, complete the device. The pitch of the screw 26b and graduations carried by the knob 29 at its periphery opposite a reference mark eventually forming a vernier scale carried by the dog 30, are such that the section of the orifice 25 which is not closed by the rod 26a can be regulated in a very precise manner (for example to the nearest hundredth of a millimeter).

It can be seen from these drawings that the pulp carried away by the cylinder (not shown) under the bar 4g, in the direction of the arrows a, passes out for the greater part, after grinding under the two lips, following the direction of the arrow b. The regulation of the leakage flow c enables the pressure to be maintained in the groove at the desired value, which remains of the order of a few kilograms per square centimetre, and which can be read from the dial of the pressure gauge combined with the bar.

It will be observed that a small fraction of the pulp passes under the bar at the two extremities, at which this latter is not provided with a groove, thus risking imperfect grinding. A reduction in the thickness of the lateral curved lips 90 of the bar and also of the portion 9d of the front lip 9a which is located on each side of the port 32 through which the pulp passes out of the hopper 2, enables the said pulp to be introduced over practically the whole of the length of the output lip 9b, thus reducing the risk of seizure in the case of high clamping pressures of the bar against the cylinder.

In practice, the operation of a mill with a single cylinder, according to the invention, is characterized by the accuracy but also by the stability of the regulation of the back-pressure in the cavity of the bar, this back-pressure being closely related to the fineness of grinding. This regulation is possible and even readily obtained irrespective of the force applied to the bar by the hydraulic clamping jacks. This force may reach high values, very much greater than those of current practice and amounting without disadvantage to and even tons. Outputs in the vicinity of 200 kilograms of pulp per hour (in the case of a pigment with a base of rutile, for example) can be obtained simultaneously with finenesses reaching 9 on the North gauge, which is remarkable. Equivalent results may be obtained irrespective of the pigments to be ground, since the clamping pressure on the bar may reach very high values.

It is also possible to make the valve 26, 26a self-regulating (see FIG. 4), by coupling the ground rod 26a to an elastic diaphragm 26c which is subjected on one of its faces to the pressure in the groove and which is rigidly fixed to a screw similar to 26b through the intermediary of an elastic member 26]), the adjustable tension of which finally determines the opening of the said valve and the fineness of grinding. No fluid-tight joint of the sliding type is necessary with this form of embodiment, which enables the pressure inside the cavity of the bar to be determined before the machine is put into operation. The elastic member may even have a calibration such that when it is set to the minimum by the knob 29, the valve maintains in the groove a back-pressure suflicient to prevent any seizure.

It will of course be understood that the invention is not limited to the forms of embodiment explicitly described but that it also covers those which can be obtained by the use of equivalent technical means.

What I claim is:

1. A cylinder bar-mill comprising a distributing hopper for the material to be ground, said hopper having an input opening and an output opening, a cylinder positioned immediately adjacent said output opening, a bar pressed against said cylinder by means of fluid actuated jacks,

said bar having two longitudinal lips separated by a groove which is closed at its extremities and which is spontaneously filled with material in the course of grinding, the width of said groove being greater than the thickness of the two lips combined, said mill being further provided with controllable discharge means for discharging the material which fills the groove, said discharge means comprising a conduit system connecting the groove of the bar to a container for the discharged material, and screw means with a micrometer thread for progressively closing said conduit system.

2. A cylinder bar-mill as claimed in claim 1, wherein the conduit system is partly constituted by a bore formed in the vicinity of the center of the bar, said screw means with a micrometer thread progressively closing said bore.

3. A cylinder bar-mill comprising a distributing hopper having both an input opening and a discharge opening and containing therein the material to be ground, a cylinder closely adjacent said discharge opening, a bar pressed against said cylinder by means of fluid actuated jacks, said bar having two longitudinally extending lips separated by a groove which is closed at its extremities and which is spontaneously filled with material in the course of grinding, the width of said groove being greater than the thickness of the two lips combined, said mill being further provided with controllable discharge means to discharge the material which fills the groove, said means comprising a conduit system connecting the groove of the bar to a container for the discharged material, a flexible wall the sides of which are respectively submitted to the action of the pressure of the material which fills the groove and to the action of an adjustable elastic calibration means, and a rod rigidly fixed to said wall and progressively controlling the opening of said conduit system in response to movements of said wall.

4. A cylinder bar-mill comprising a distributing hopper containing the material to be ground and having both input and discharge openings, a cylinder mounted adjacent said discharge opening, a bar pressed against said cylinder by means of fluid actuated means, said bar having two lips separated by a groove which is closed at its extremities and which is spontaneously filled with material in the course of grinding, the width of said groove being greater than the thickness of the two lips combined, said mill being further provided with controllable discharge means for the material Which fills the groove, said means comprising a conduit system connecting the groove of the bar to a container for the discharged material, and a volurnetric pump disposed in the conduit system and driven 1n rotation by the cylinder of said mill.

5. A cylinder bar-mill as claimed in claim 4, wherein the container for the discharged material is the hopper of the mill.

References Cited by the Examiner UNITED STATES PATENTS 3,206,129 9/1965 Brizon 241-241 FOREIGN PATENTS 66,312 9/1938 Germany. 494,636 10/1938 Great Britain.

WILLIAM W. DYER, JR., Primary Examiner.

a H. F. PEPPER, Assistant Examiner. 

1. A CYLINDER BAR-MILL COMPRISING A DISTRIBUTING HOPPER FOR THE MATERIAL TO BE GROUND, SAID HOPPER HAVING AN INPUT OPENING AND AN OUTPUT OPENING, A CYLINDER POSITIONED IMMEDIATELY ADJACENT SAID OUTPUT OPENING, A BAR PRESSED AGAINST SAID CYLINDER BY MEANS OF FLUID ACTUATED JACKS, SAID BAR HAVING TWO LONGITUDINAL LIPS SEPARATED BY A GROOVE WHICH IS CLOSED AT ITS EXTREMITIES AND WHICH IS SPONTANEOUSLY FILLED WITH MATERIAL IN THE COURSE OF GRINDING, THE WIDTH OF SAID GROOVE BEING GREATER THAN THE THICKNESS OF THE TWO LIPS COMBINED, SAID MILL BEING FURTHER PROVIDED WITH CONTROLLABLE DISCHARGE MEANS FOR DISCHARGING THE 